abstraction-download, in Python

A download that outlives the process that asked for it. What was asked for, how far it got and who may work on it live in a record on disk, so a transfer this process starts, the next launch — or another machine — can finish. Standard library only.

This page is the Python package. The contract, the Go and C++ implementations, what is measured and what is UNPROVEN are on the repository.

Install

Not on PyPI, and the names on PyPI are not ours. Clone the five repositories beside each other and install them in dependency order:

git clone https://github.com/openabstractions/abstraction-cas
git clone https://github.com/openabstractions/abstraction-watch
git clone https://github.com/openabstractions/abstraction-job
git clone https://github.com/openabstractions/abstraction-config
git clone https://github.com/openabstractions/abstraction-download

pip install ./abstraction-cas/python ./abstraction-watch/python
pip install ./abstraction-job/python ./abstraction-config/python
pip install ./abstraction-download/python

Python 3.9 or later. The order is not a style: pyproject.toml names these dependencies by the names they would have on an index, and pip can only satisfy them from what is installed already.

Copying the modules works too, and is the route the one shipped adopter takes. abstraction_cas.py, abstraction_watch.py, abstraction_job.py, abstraction_config.py and abstraction_download.py are pure standard library, so a _vendor/ directory of your own is a complete installation — see adopter-comfyui.

An example that runs

import abstraction_download as dl

svc = dl.discover()
print("who would fetch this:", svc.where())

job = svc.get("https://raw.githubusercontent.com/openabstractions/abstractions/main/LICENSE", "LICENSE.txt")
record = svc.deliver(job)
print("bytes are at:", dl.spec_of(record).sink.final)

Nothing needs configuring and no service needs to be running. On a machine with neither it prints who would fetch this: here and the path the file landed at. get returns a job id at once and the transfer may outlive this call and this process; deliver waits for the bytes and takes delivery, which is what a caller that reads the file on the next line needs. where names who would take the next job — here, bits, nas, nobody — as text for a status line, not a value to branch on.

Your application was closed mid-transfer. This is the next launch finishing what nobody is working on, before it asks for anything new:

import abstraction_download as dl

print("resumed:", dl.discover().runner.adopt())

What an application calls

A Spec is what to fetch: an Artifact (digest, size), an ordered list of Source locators, and a Sink naming where the bytes go.

dl.Spec(
    artifact=dl.Artifact(digest="sha256:...", size=328597408),
    sources=[dl.Source(scheme="https", locator="https://...")],
    sink=dl.Sink(final="models/x.gguf"),
)

Capabilities requires accepts: dl.CAP_RESUME, dl.CAP_SURVIVES_PROCESS_EXIT, dl.CAP_VERIFIES, dl.CAP_DELEGATES. Every normative rule is on CONTRACT.md, tagged; none is restated here.

What may break

• The bytes are fetched by this process and they stop when it stops. They resume when it starts again; nothing arrives while your application is closed. Requiring CAP_SURVIVES_PROCESS_EXIT from Python is refused, not silently downgraded — that needs service-jobd, which is a Go binary a Python application cannot ship.
• No tagged release and no package index. Pin a commit you have read.
• watch, which this depends on, carries no conformance verdict. What is proven and what is not.
• Every published transcript was produced on Windows or Linux. macOS is UNPROVEN throughout.

Apache-2.0. See LICENSE.